In the past, parallel axis type gear measuring apparatuses measured parameters of a work gear by measuring a change in a center distance between the rotation axes of the work gear and a master gear, wherein the change in center distance was monitored by a mechanical gauge. The change in center distance, however, is a composite signal resulting from many parameters of the work gear and had limited value. The composite signal results from the engagement of more than one tooth of the work gear by the master gear, wherein the change in center distance was a result of measurement components from several teeth of the work gear at one time. More recently, it has been suggested to convert the change in center distance to an electrical signal, wherein the components of the electrical signal are separated by electronically filtering the signal, over different frequency ranges, into its component signals. The component electrical signals correspond to various parameters of the work gear, and therefore provide more precise measurement information about the work gear. For example, the component electrical signals provide measurement information on lead error, nicks, gear size, runout, bore size, angular velocity error, and gear face squareness. Parameters derived by electronic filtering, however, have a limited accuracy, and require costly electronic equipment. Further, the automated gear measurements discussed above do not provide any information on tooth profile, which has generally been measured using time consuming and costly analytical techniques.
In view of the discussion above, there exists a demonstrated need for an advancement in the art of a master gear for checking a work gear, and, in particular, for a master gear that quickly and economically measures gear parameters including tooth profile.
It is therefore an object of the present invention to provide a novel master gear for measuring a work gear in a parallel axis gear measuring apparatus.
It is another object of the present invention to provide a novel master gear that measures tooth profile, tooth pitch, and tooth thickness of the work gear.
It is a further object of the present invention to provide a novel master gear for quickly and economically measuring a work gear, wherein work gear parameters may be measured for each tooth or, in the alternative, may be averaged.
It is also an object of the present invention to provide a novel master gear that contacts only a single tooth of the work gear during measurement of work gear tooth profile and tooth thickness, wherein the measurement is not affected by contact between other teeth of the work gear and the master gear.
It is yet another object of the present invention to provide a novel master gear that contacts only two teeth of the work gear to provide a continuous, smooth, transition between engagement of individual teeth for measurement of tooth profile, wherein tooth pitch is measured during the transition.
It is another object of the present invention to provide a master gear that has a transverse operating pressure angle that depends on a transverse pressure angle at an outer diameter of the work gear, a transverse pressure angle at a form diameter of the work gear, a transverse pressure angle at a pitch diameter of the work gear, a transverse tooth thickness at a pitch diameter of the work gear, and a pitch diameter of the work gear.
It is a further object of the present invention to provide a novel master gear having helical teeth for measuring a work gear having helical teeth, wherein the master gear has a minimum width and tooth spacing that depends on a gear contact ratio.
It is yet a further abject of the present invention to provide a novel master gear having spur teeth for measuring a work gear having spur teeth.
Accordingly, the present invention is directed toward a novel master gear for measuring, in a parallel axis gear measuring apparatus, tooth profile, tooth pitch, and tooth thickness of a work gear. The master gear includes a plurality of adjacent teeth separated by a tooth spacing that varies as a repeatable sequence of spacings, wherein the master gear contacts only a single tooth of the work gear during measurement of work gear tooth profile and tooth thickness. The master gear contacts only two teeth of the work gear during a transition between measurement of tooth profile on teeth of the work gear, wherein tooth pitch is measured during the transition. The master gear has a transverse operating pressure angle dependent on a transverse pressure angle at an outer diameter of the work gear, a transverse pressure angle at a form diameter of the work gear, a transverse pressure angle at a pitch diameter of the work gear, a transverse tooth thickness at a pitch diameter of the work gear, and a pitch diameter of the work gear. In one embodiment, the master gear has helical teeth having a tooth spacing dependant on a contact ratio of the work gear. The width of the master gear with helical teeth is dependent on an involute contact ratio of the work gear, a number of teeth in the work gear, a normal diametral pitch, a helix angle of the work gear, and a factor that compensates for frictional wear on the master gear. In another embodiment, the master gear has spur teeth for measuring a work gear having spur teeth. The master gear having spur teeth is further defined by parameters relating to a pressure angle of an imaginary outer diameter of the work gear and a pressure angle of an imaginary form diameter of the work gear. The additional parameters depend on an involute contact ratio of the work gear, a pressure angle at an outer diameter of the work gear, a pressure angle at a form diameter of the work gear, a generating pressure angle of the work gear, a number of teeth on the work gear, a pitch diameter of the work gear, a tooth thickness at a pitch diameter of the work gear, a pressure angle of an imaginary outer diameter of the work gear, and a pressure angle of an imaginary form diameter of the work gear.
These and other objects, features and advantages of the present invention will become apparent upon consideration of the following Detailed Description of the Invention with the accompanying drawings.